AD7664_15 Datasheet, PDF (7/24 Pages) Analog Devices – 16-Bit, 570 kSPS

Pin No. Mnemonic
35
CNVST
36
AGND
37
REF
38
REFGND
39
INGND
43
IN
NOTES
AI = Analog Input
DI = Digital Input
DI/O = Bidirectional Digital
DO = Digital Output
P = Power
AD7664
Type
DI
P
AI
AI
AI
AI
Description
Start Conversion. A falling edge on CNVST puts the internal sample-and-hold into the hold state
and initiates a conversion. In Impulse Mode (IMPULSE HIGH and WARP LOW), if CNVST is
held LOW when the acquisition phase (t₈) is complete, the internal sample-and-hold is put
into the hold state and a conversion is immediately started.
Must Be Tied to Analog Ground.
Reference Input Voltage.
Reference Input Analog Ground.
Analog Input Ground.
Primary Analog Input with a Range of 0 V to V_REF.
DEFINITION OF SPECIFICATIONS
Integral Nonlinearity Error (INL)
Linearity error refers to the deviation of each individual code
from a line drawn from negative full scale through positive full
scale. The point used as negative full scale occurs 1/2 LSB
before the first code transition. Positive full scale is defined as a
level 1 1/2 LSB beyond the last code transition. The deviation is
measured from the middle of each code to the true straight line.
Differential Nonlinearity Error (DNL)
In an ideal ADC, code transitions are 1 LSB apart. Differential
nonlinearity is the maximum deviation from this ideal value. It is
often specified in terms of resolution for which no missing codes
are guaranteed.
Full-Scale Error
The last transition (from 011 . . . 10 to 011 . . . 11 in twos
complement coding) should occur for an analog voltage 1 1/2 LSB
below the nominal full scale (2.49994278 V for the 0 V–2.5 V
range). The full-scale error is the deviation of the actual level of
the last transition from the ideal level.
Unipolar Zero Error
The first transition should occur at a level 1/2 LSB above analog
ground (19.073 µV for the 0 V–2.5 V range). Unipolar zero
error is the deviation of the actual transition from that point.
Spurious-Free Dynamic Range (SFDR)
The difference, in decibels (dB), between the rms amplitude of
the input signal and the peak spurious signal.
Effective Number of Bits (ENOB)
ENOB is a measurement of the resolution with a sine wave
input. It is related to S/(N+D) by the following formula:
( ) [ ] ENOB = S N + D − 1.76 6.02
dB
and is expressed in bits.
Total Harmonic Distortion (THD)
THD is the ratio of the rms sum of the first five harmonic
components to the rms value of a full-scale input signal and is
expressed in decibels.
Signal-to-Noise Ratio (SNR)
SNR is the ratio of the rms value of the actual input signal to
the rms sum of all other spectral components below the Nyquist
frequency, excluding harmonics and dc. The value for SNR is
expressed in decibels.
Signal to (Noise + Distortion) Ratio (S/[N+D])
S/(N+D) is the ratio of the rms value of the actual input signal to
the rms sum of all other spectral components below the Nyquist
frequency, including harmonics but excluding dc. The value for
S/(N+D) is expressed in decibels.
Aperture Delay
Aperture delay is a measure of the acquisition performance and
is measured from the falling edge of the CNVST input to when
the input signal is held for a conversion.
Transient Response
The time required for the AD7664 to achieve its rated accuracy
after a full-scale step function is applied to its input.
Overvoltage Recovery
The time required for the ADC to recover to full accuracy after
an analog input signal 150% of full-scale is reduced to 50% of
the full-scale value.
REV. E
–7–